The field of invention relates generally to micro and/or nano-fabrication of structures. More particularly, the present invention is directed to forming relief structures in substrates.
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has a sizeable impact is in the semiconductor processing industry for the manufacture of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.
Traditional micro-fabrication employs photolithography techniques to replicate patterns on substrates. Photolithography includes a combination of an exposure tool and an image transfer process. To that end, a process compatible masking layer, often referred to as a resist-layer, is employed to provide the desired pattern. That is, the material from which the resist-layer is fabricated is optimized for the exposure tool and the image transfer process. As a result, several factors are considered when determining the proper resist material, including the exposure wavelength and compatibility of the resist-layer material to post imaging processes, e.g., subsequent etch and deposition processes. In addition to the resist-layer, replicating patterns with well-defined features is dependent upon operational characteristics of the exposure tool. These characteristics include, and are not limited to, the numerical aperture of the exposure tool lens, wavelength employed and alignment systems.
Recently a new non-photolithographic patterning process has evolved, which is commonly referred to as imprint lithography, overcoming many of the complexities and limitations of exposure tool technology. Exemplary imprint lithographic processes are described in detail in numerous publications, such as United States published patent application 2004/0065976, filed as U.S. patent application Ser. No. 10/264,960 on Oct. 4, 2002 and entitled METHOD AND A MOLD TO ARRANGE FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL DIMENSIONAL VARIABILITY; United States published patent application 2004/0065252, filed as U.S. patent application Ser. No. 10/264,926 on Oct. 4, 2002 and entitled METHOD OF FORMING A LAYER ON A SUBSTRATE TO FACILITATE FABRICATION OF METROLOGY STANDARDS; and United States published patent application 2004/0046271, filed as U.S. patent application Ser. No. 10/235,314 on Sep. 5, 2002 and entitled FUNCTIONAL PATTERNING MATERIAL FOR IMPRINT LITHOGRAPHY PROCESSES, all of which are assigned to the assignee of the present invention.
The fundamental imprint lithography technique disclosed in each of the aforementioned published patent applications includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer.
Generally, control over the dimensions of the features formed with the aforementioned processes has been dependent upon the topology of the underlying surface in contact with the formable liquid. The greater anisotropy of the surface the greater the distortion in the relief image.
There is a need, therefore, to provide improved processes for forming relief structures on substrates containing topography.